Constraint-based ACO for a shared resource constrained scheduling problem

We consider a scheduling problem arising in the mining industry. Ore from several mining sites must be transferred to ports to be loaded on ships in a timely manner. In doing so, several constraints must be met which involve transporting the ore and deadlines. These deadlines are two-fold: there is a preferred deadline by which the ships should be loaded and there is a final deadline by which time the ships must be loaded. Corresponding to the two types of deadlines, each task is associated with a soft and hard due time. The objective is to minimize the cumulative tardiness, measured using the soft due times, across all tasks. This problem can be formulated as a resource constrained job scheduling problem where several tasks must be scheduled on multiple machines satisfying precedence and resource constraints and an objective to minimize total weighted tardiness. For this problem we present hybrids of ant colony optimization, Beam search and constraint programming. These algorithms have previously shown to be effective on similar tightly-constrained combinatorial optimization problems. We show that the hybrid involving all three algorithms provides the best solutions, particularly with respect to feasibility. We also investigate alternative estimates for guiding the Beam search component of our algorithms and show that stochastic sampling is the most effective.     

Using flexible schedules in the managerial world: The power of peers

Reports indicate that managers fail to take advantage of flexible work schedules to integrate work and life demands. A survey was conducted of approximately 1,000 managers who had three alternative schedule options: flextime, part‐time work, and leave of absence. Managers who were women or who had work group peers who were schedule users were more likely to use each schedule. Managers' productivity concerns were highest for flextime, then leaves, and least for part‐time work. Organizational cultural change can occur if managers take the lead in their work groups to use flexible schedules in order to remove social barriers. © 1999 John Wiley & Sons, Inc.     

The impact of monetary policy surprises on asset return volatility: the case of Germany

This paper investigates the impact of monetary policy surprises by the FED or Bundesbank/ECB on the return volatility of German stocks and bonds using a GARCH-M model. We show that stock return volatility is susceptible to monetary policy surprises in the United States, whereas monetary policy surprises in the Euro zone matter for bond return volatility. These findings are robust for other Euro zone stock markets, but not significant for other Euro zone bond markets. The empirical evidence also suggests that monetary policy surprises have larger effects on German stock return volatility in bear markets than in bull phases. Moreover, our results support the claim that stock return volatility can be negatively correlated with stock returns, contradicting predictions made by many asset pricing models (e.g., CAPM or ICAPM) and the empirical finding of an insignificant relationship often reported in the literature.

The perspectives of the North-South Dialogue

During the 1970s the North-South Dialogue, which will shortly be continued at the summit in Mexico, was characterized by a gross disproportion between monstrous expenditure—with many losses due to friction —and negligible results. Symptoms of fatigue with regard to the Dialogue are spreading not only among governments, but also among the public in the North. The disillusionment and disappointment are proportionally greater in the South. As no one would presumably like to risk a failure of the Dialogue, which would probably result in a severe aggravation of the North-South conflict, a reorientation of the Dialogue now suggests itself.     

How Fundamental are Fundamental Values? Valuation Methods and their Impact on the Performance of German Venture Capitalists

This paper studies how the use of alternative valuation methodologies affects investment performance for a sample of 53 German venture capitalists. We measure investment performance by the amount of investments they need to write off and by the number of companies they take public. We find that a significant number of investment managers use discounted cash flow (DCF) techniques, but only a minority appears to use a discount rate related to the cost of capital. The majority applies DCF using subjective discount rates. We present evidence that the use of DCF is correlated with superior investment performance only if applied in conjunction with an objectifiable discount rate. Also, funds that invest with a longer horizon perform better. The use of multiples is not significantly correlated with investment performance. We conclude that a focus on fundamental values confers an advantage.     

How Teamwork Matters More as Team Member Dispersion Increases*

Product development teams become increasingly dispersed because innovative project tasks require the input of specialized knowledge at multiple locations. Prior analyses indicate that as team member dispersion increases teams find it more difficult to perform high‐quality teamwork. Moreover, the literature has largely assumed that the performance effect of teamwork in innovative projects would be driven by the nature of the project task and that this would be true regardless of the degree to which team members were co‐located. The present study argues, however, that teamwork affects team performance more strongly as team member dispersion increases. Two main reasons for this are discussed: (1) High‐quality teamwork can leverage the increased knowledge potential of dispersed teams; and (2) team leaders in more dispersed teams have little possibility to compensate low‐quality teamwork through hands‐on leadership. Responses from 575 managers, team leaders, and team members of 145 new product development (NPD) projects in the software industry were used to analyze the moderating effect of team member proximity on the relationship between teamwork quality and team performance. Using regression analysis, support is found for the initial hypothesis that team member dispersion moderates the relationship between teamwork quality and team performance, that is, that increasing team member dispersion increases the positive impact of teamwork quality on team performance. As such, the present analysis advances understanding of dispersed teams, showing that teamwork quality not only is more difficult to achieve but also is more critical to team performance as team dispersion increases. Furthermore, low‐proximity teams can reach higher levels of effectiveness and efficiency than co‐located ones if they manage to achieve high levels of teamwork over distance. Thus, team dispersion may well be an opportunity and should not just be regarded as a liability to be overcome or avoided. This research recognizes that the vast majority of teams are neither perfectly co‐located nor perfectly virtual. There are many shades of gray between these two extremes, and various individual, team, task, and contextual characteristics may have an effect on how decreases—however small—in geographical proximity affect the process and performance of teams. Future research is encouraged to address such factors at different levels of analysis aimed at providing managers with recommendations for dispersed teamwork.     

Energy use,technical progress and productivity growth: A survey of economic issues

In this paper I survey and interpret several of the most important aspects underlying relationships among technical progress, productivity growth, and energy use, viewed from the vantage of an economist. The first portion of the paper provides a noneconomist with a nontechnical summary of the economic theory of cost and production, and defines single-factor and multi-factor productivity growth. In the second half of the paper, four examples are presented that highlight the special role of energy consumption in inducing and reflecting the effects of technical progress and productivity growth. A common theme in the four examples is that the concepts of embodiment, diffusion and learning are critical to understanding the forces linking energy usage, technical progress and productivity growth.The refereeing process of this paper was handled through T.G. Cowing.